The present invention relates to a pressure sensor. In particular, the invention relates to a diaphragm pressure sensor which is suspended to provide stress isolation,
The prior art shows various solid state pressure sensors which have a deflectable diaphragm for sensing pressure. Some are capable of being formed by batch processing. It is desirable to have solid state pressure sensors made of relatively rigid materials, such as semiconductor materials, and yet have them "hard mounted" which means that they have a mounting surface non-resiliently mounted onto a supporting surface. It is also desirable to have the sensing element completely surrounded by the fluid pressure being measured and to have the entire sensor and supporting structure constructed of the same material. This type of construction will minimize errors caused by line pressure variations. In other words, the sensor will respond to differential pressure but be insensitive to changes in common pressure. During operation, such sensors are frequently subjected to strain from external sources. Difficulty has been encountered in minimizing the effects of external strain on the support surface, which is a source of unwanted stress on the measuring diaphragm. This provides false or inaccurate pressure readings. U.S. Pat. No. 4,612,599, issued Sep. 16, 1986, entitled "Capacitive Pressure Sensor," shows a pressure sensor formed with silicon. U.S. Pat. No. 4,800,758, issued Jan. 3, 1989, entitled "Pressure Transducer with Stress Isolation for Hard Mounting" describes a batch fabricated pressure sensor with stress isolation.